O. mutabilis Klebs: Ovoid to spherical; plastic;
15-30 μm long,
8-22 μm wide (Kudo, 1966).
Resembles Chromulina; 1-2 chloroplasts; usually a stigma (How to know the protozoa, 1979).
O. granularis Doflein: 5-12 μm long;
no stigma (Kudo, 1966).